1. Field of the Invention
This invention relates to an air-conditioning and hot-water supplying system having a prime mover adapted to drive a compressor disposed in a heat pump circuit, and more particularly, to such an air-conditioning and hot-water supplying system capable of recovering heat discharged from the prime mover for the utilization thereof as an auxiliary heat source for heating air as well as a heat source for heating water to be stored in a hot-water tank.
2. Description of the Prior Art
In general, there have been known two types of prime mover driven air-conditioning and hot-water supplying systems of the kind described above, one for directly introducing cooling water heated by a prime mover into an indoor radiator installed in a building or housing where the heat is radiated from the radiator so as to heat the air in the housing, and the other for heating cooling medium circulating through a heat pump circuit by means of prime-mover cooling water and utilizing the cooling medium thus heated for heating the interior of a building or housing.
FIG. 9 shows a circuit arrangement of a conventional prime mover driven air-conditioning and hot-water supplying system of the latter type in which a heat-transmitting medium such as a gaseous cooling medium circulating through a heat pump circuit is heated by cooling water for the prime mover. The conventional air-conditioning and hot-water supplying system as illustrated comprises a heat pump circuit 30 for air conditioning, a hot-water circulation circuit 31, a prime mover cooling circuit 32 for water cooling a prime mover 1, and a heat-pump water-heating circuit 34 for heating water in the hot-water circulation 31 under the heat pump operation of the heat pump circuit 30.
The heat pump circuit 30 includes a compressor 3 operably connected through a clutch 2 with the prime mover 1 in the form of a water-cooled engine, a four-way directional control valve 4 connected to the compressor 3, an indoor heat exchanger 5 connected through an electromagnetic change-over valve 15 to the four-way directional control valve 4 and installed inside a housing for exchanging heat between a heat-transmitting medium in the heat pump circuit 30 and air in the housing, an indoor fan 6 attached to the indoor heat exchanger 5, an indoor heat exchanger 7 installed outside the housing for exchanging heat between the heat-transmitting medium in the heat pump circuit 30 and air outside the housing, an outdoor fan 8 attached to the outdoor heat exchanger 7, a receiver 9 connected to the outdoor heat exchanger 7 through a check valve 11 and to the indoor heat exchanger 5 through a check valve 12 and adapted to store condensed heat-transmitting medium circulating through the heat pump circuit 30, a throttling means 10 such as an expansion valve or the like connected to the receiver 9 and to the outdoor heat exchanger 7 through a check valve 13 and to the indoor heat exchanger 5 through a check valve 14, and a pump 26 adapted to be driven to circulate the heat-transmitting medium in the heat pump circuit 30. The compressor 3, the indoor heat exchanger 5, the outdoor heat exchanger 7, the receiver 9, the throttling means 10 and the pump 26 are connected with each other through pipings so that the heat-transmitting medium is forced to circulate through these members for air conditioning the interior of the housing.
The hot-water circulation circuit 31 comprises a hot water tank 19 connected at its lower portion through a water feed pipe 21 to a source of water (not shown) and at its top to the hot water tap 22 for dispensing the hot water stored in the hot water tank 19; and a pump 20 connected at its one side to a lower portion of the hot water tank 19 and at its other side to the top of the hot water tank 19 through heat exchangers 17 and 18 to be described in detail later so that water supplied to the hot water tank 19 from the water source (not shown) through the water feed pipe 21 is forced by means of the pump 20 to circulate through the heat exchangers 17, 18 and the hot water tank 19 while being heated by the heat exchangers 17, 18.
The heat-pump water-heating circuit 34 comprises the heat exchanger 17 connected to the four-way directional control valve 4 in the heat pump circuit 30 through an electromagnetic change-over valve 16 and to the receiver 9 through a check valve 12 in the heat pump circuit 30 for exchanging heat between the heat-transmitting medium and water in the hot-water circulation circuit 31.
The prime mover cooling circuit 32 comprises a pump 23, a water jacket (not shown) in the prime mover 1 connected to the pump 23, and the heat exchanger 18 connected to the pump 23 and to the water jacket (not shown) in the prime mover 1 through an electromagnetic change-over valve 24, the heat exchanger 18 being also connected to the heat exchanger 17 and the hot water tank 19 in the hot-water circulation circuit 31 for exchanging heat between the cooling water in the prime mover cooling circuit 32 and the water in the hot-water circulation circuit 31. A sensor 35 is arranged between the heat exchanger 18 and the electromagnetic change-over valve 24 for sensing the temperature of the cooling water circulating through the prime mover cooling circuit 32.
The heat-transmitting-medium heating circuit 33 is connected with the prime mover cooling circuit 32 in a parallel relation with the heat exchanger 18 and comprises a heat exchanger 27 connected to the pump 23 and to the water jacket in the prime mover 1 through an electromagnetic change-over valve 25, the heat exchanger 27 being also connected at its one side to the receiver 9 through a pump 26 and at its other side to the heat pump circuit 30 through a check valve 28 at a location between the four-way directional control valve 4 and the electromagnetic change-over valves 15 and 16 for heating the heat-transmitting medium circulating through the heat pump circuit 30 by means of the prime mover cooling water heated by the prime mover 1.
In operation, by changing over the four-way directional control valve 4 in an appropriate manner, the conventional air-conditioning and hot-water supplying system is changed between a cooling operation mode and a heating operation mode. When the system is changed to a cooling operation mode, heat-transmitting medium is discharged from the compressor 3 driven by the engine 1 to flow through the four-way directional control valve 4, the check valve 11, the receiver 9, the expansion valve 10, the check valve 14, the indoor heat exchanger 5, the electromagnetic change-over valve 16 and the four-way directional control valve 4, thus returning to the compressor 3. In the course of circulation of the heat-transmitting medium through the heat pump circuit 30, heat of the heat transmitting medium is radiated to the outside by means of the outdoor heat exchanger 7 so that the heat transmitting medium is thereby cooled, whereas the heat-transmitting medium thus cooled absorbs heat from the air in the interior of the housing under the action of the indoor heat exchanger 5, thus cooling the air in the housing.
On the other hand, where the air-conditioning and hot-water supplying system is changed over to a heating mode, the heat-transmitting medium discharged from the compressor 3 flows through the four-way directional control valve 4, the electrpmagnetic change-over valve 15, the indoor heat compressor 5, the check valve 12, the receiver 9, the expansion valve 10, the check valve 13 and the outdoor heat exchanger 7 and the four-way directional controm valve 4, returning to the compressor 3. During such circulation of the heat-transmitting medium through the heat pump circuit 30, the heat-transmitting medium of a low temperature absorbs heat from the outside air under the heat-exchanging action of the outdoor heat exchanger 7, and the heat thus absorbed by the heat-transmitting medium is then radiated to the air inside the housing under the action of the indoor heat exchanger 7, thereby heating the interior of the housing.
When the electromagnetic change-over valve 15 in the heat pump circuit 30 is closed and the electromagnetic change-over valve 16 is opened in the heating operation mode of the system, the heat-transmitting medium discharged from the compressor 2 through the four-way directional control valve 4 flows through the electromagnetic change-over valve 16 and the heat exchanger 17 in the heat-pump water-heating circuit 34, and thence through the check valve 12, the receiver 9, the expansion valve 10, the check valve 13, the outdoor heat exchanger 7 and the four-way directional control valve 4 into the compressor 3 so that water, being fed to the tank 19 from a source of water (not shown) via the water feed pipe 21 and forced by the pump 20 to circulate through the heat exchangers 17, 18, is heated by the heat-transmitting medium flowing through the heat-pump water-heating circuit 34 under the action of the heat exchanger 17.
In this case, in the cooling or heating operation mode of the system, the prime mover 1, being operated to drive the compressor 3, must be cooled. Specifically, by driving the cooling water pump 23, cooling water is forced to circulate through the prime mover cooling circuit 32, that is the cooling water discharged from the pump 23 flows successively through the water jacket (not shown) in the prime mover 1, the electromagnetic change-over valve 24 and the heat exchanger 18 and returns to the pump 23. Thus, in the course of circulation of the cooling water through the prime mover cooling circuit 32, the cooling water passing through the water jacket in the prime mover 1 absorbs the heat generated in the prime mover 1 and cools it. On the other hand, the cooling water thus heated by the prime mover 1 passes through the heat exchanger 18 so that it heats water circulating through the hot-water circulation circuit 31 under the action of the heat exchanger 18. Accordingly, in this case, water circulating through the hot-water circulation circuit 31 is heated by utilizing heat generated in the prime mover 1 which otherwise would be wasted (hereinafter referred to as waste heat).
Hot water to be stored in the hot water tank 19 successively circulates from the hot water tank 19 through the hot-water circulation pump 20, the heat exchanger 17, the heat exchanger 18 and back to the tank 190. Since the electromagnetic change-over valve 16 is closed during the cooling or heating operation mode of the system, the water circulating through the hot-water circulation circuit 31 is heated only by the heat exchanger 18. On the other hand, in the heat-pump hot-water supplying operation of the system, the electromagnetic change-over valve 15 in the heat pump circuit 30 is closed and the electromagnetic change-over valve 16 is opened so that water circulating through the hot-water circulation circuit 31 is heated by both of the heat exchangers 17 and 18. In this regard, during the operation of the prime mover 1, the hot-water circulation pump 20 is always driven to run so as to utilize the waste heat generated in the prime mover 1.
Although the normal cooling or heating operation of the system is effected in the above-described manner, cooling water in the prime mover cooling circuit 32 is introduced into the heat-transmitting-medium heating circuit 33 by opening the electromagnetic change-over valve 25 and closing the electromagnetic change-over valve 24 so that the cooling water discharged from the cooling water pump 23 flows through the water jacket in the prime mover 1 and the electromagnetic change-over valve 25 into the heat exchanger 27, and returns to the cooling water pump 23 in cases where the heating load is great during the heating operation of the system or where the hot water stored in the hot water tank 19 has been heated to a high temperature and at the same time, the cooling water passing through the water jacket of the prime mover 1 is raised in its temperature so that the heat absorbed by the cooling water from the prime mover 1 can not be radiated from the heat exchanger 18 to any satisfactory extent. Simultaneous with this change-over operation of the electromagnetic valves 24 and 25, the pump 26 is actuated to run so that the heat-transmitting medium cooled by the indoor heat exchanger 5 is introduced from the receiver 9 into the pump 26 which in turn discharges the cooled heat-transmitting medium toward the heat exchanger 27. The heat-transmitting medium thus discharged from the pump 26 passes through the heat exchanger 27 and absorbs the heat from the prime mover cooling water passing therethrough so that it is thereby heated up and at the same time cools the cooling water. In this manner, the temperature of the cooling water is lowered by the heat exchanger 27. The heat-transmitting medium thus heated by the heat exchanger 27 passes through the check valve 28 and merges with the heat-transmitting medium discharged from the compressor 3 through the four-way directional control valve 4 so that the heat transmitting medium thus merged flows through the electromagnetic change-over valve 15 into the indoor heat exchanger 5 where the heat of the heat transmitting medium is radiated to heat the air in the housing. Thus, an increased heating capacity is obtained at the indoor heat exchanger 5. As a result, in spite of the fact that in the normal heating operation under the heat-pump operation mode of the system, the heating capacity is reduced when the temperature of the outside air is low, such a reduction in heating capacity is effectively compensated for by utilizing the waste heat generated in the prime mover 1 to heat the heat-transmitting medium supplied to the indoor heat exchanger 5 as referred to above, the amount of such waste heat of the prime mover 1 being constant irrespective of the ouside temperature.
In the event that the temperature of the hot water stored in the hot water tank 19 rises to such an extent that the cooling water for cooling the prime mover 1 can not be cooled by the water circulating through the hot-water circulation circuit, the sensor 35 detects such a high temperature of the cooling water so that the electromagnetic change-over valves 24 and 25 are closed and opened, respectively, to circulate the cooling water through the heat exchanger 27 in place of the heat exchanger 18.
With a conventional air-conditioning and hot-water supplying system as constructed above, however, the heat exchanger 27 for exchanging heat between the cooling water for cooling the prime mover 1 and the heat-transmitting medium circulating through the heat pump circuit 30, and the heat exchanger 18 for exchanging heat between the water in the hot-water circulation circuit 31 and the cooling water in the prime mover cooling circuit 32 are incorporated in or connected to the prime mover cooling circuit 32 in a parallel relation with each other such that in the normal heating or cooling operation of the system, the electromagnetic change-over valves 24 and 25 are opened and closed, respectively, whereas when a greater heating capacity is required, the electromagnetic change-over valves 24 and 25 are closed and opened, respectively, so as to introduce the cooling water for cooling the prime mover 1 into the heat exchanger 27 so as to heat the heat-transmitting medium fed into the indoor heat exchanger 5. In order to achieve such a function, provision is needed for the electromagnetic change-over valves 24 and 25 and the sensor 35 as well as piping arrangements and installation spaces for the heat exchangers 18 and 27, thus resulting in an increase in the overall dimensions and weight of the entire air-conditioning and hot-water supplying system.
In particular, the above-described conventional air-conditioning and hot-water supplying system having a compressor driven by a prime mover is superior in running cost to an air-conditioning and hot-water supplying system driven by an electric motor, but disadvantageous in the weight and required installation space thereof since the prime mover and the related auxiliary equipment are needed and hence the weight and required installation space become larger as compared with those for an air-conditioning and hot-water supplying system driven by an electric motor. In addition, to heat the heat-transmitting medium by the use of the waste heat generated in the prime mover for improved heating capacity results in an increase in number of heat exchangers as well as an increase in the weight and manufacturing cost of the entire system.